wedge an air hammer into the valve cover while prying on the contra lateral vertex of the distributor with the largest pry bar you can find

or

as a last resort, wear some mech gloves, grip the hell out of that shit and yank it off ...(someone rounded the hell out of the screw on one of the cars i've worked on and i had to do this...the rotor breaks pretty easily, then you just take some needle nose and turn the screw out)--there might be less creative ways that works better...but like i said....last resort